delayed_paperclip and Ajax
Use delayed_paperclip to process Paperclip attachments in the background. Use Rails routes and Ajax to check when processing is done.
Live app which you can run on the fly: http://runnable.com/VR3XZVDPXUJ0k3VQ/paperclip-delayed-job (remember to run bin/delayed_jobs start
before clicking the big green Run button)
app/models/photo.rb